The use of a piezoelectric actuator as a means for converting electric power into mechanical power is widely known. For instance, such a piezoelectric actuator may be conveniently used to control a fuel injection valve of an internal combustion engine. This is advantageous, since a piezoelectric actuator has a faster response than a conventional electromagnetic solenoid. Accordingly, control of the fuel injection valve is performed by utilizing the responsive characteristics of the piezoelectric actuator.
It is necessary to provide a drive circuit for controlling the piezoelectric actuator by supplying a voltage to the actuator. Since a piezoelectric actuator requires a relatively high drive voltage, a power source which can supply a sufficiently high voltage is required. When such a high voltage power source is not used, a drive circuit that can boost the drive voltage to the required high level is needed. The later is the conventional approach.
Conventional piezoelectric driver circuits use an LC frequency design. This type of design "matches" an inductor to a capacitor to obtain a voltage doubling effect. However, large inductance and capacitance values are required to double the voltage value. Large inductors and capacitors are undesirable because of the large amount of space that the inductor and capacitor require.
The present invention is directed to overcoming one or more of the problems as set forth above.